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Half Scale B-25

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vhhjr

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This thread was started up in the new member area and really should be here with all the other Walter Mitty designed aircraft. Building a scale B-25 Mitchell has been mentioned in other forums and has always been interesting to me. I looked at smaller scales and 50% is about the lower limit if you want scale outlines and the possibility of a passenger. The interior of a full scale B-25 is rather cramped so at 50% it would be a tandem seating arrangement. If the engine nacelles are enlarged by an inch or so either Verner or Rotec radials would fit. A lower cost option would be Jabiru 3300 that are much more available in the used market. One wants controllable pitch props on a twin and I'm still researching those items.

This is the third cockpit mock up that I have built. The 70% P-39 was a fun project and showed it to be the right scale whereas the 55% ME-262 was too small and should have been at least 65% to fit pilots with a more "mature" physique. As with the others, the B-25 is from an enlarged Giant Scale RC plan, in this case a 1/6th scale version by Ziroli. There are such plans available for most any plane you can think of. I had a digital file of the plans and using Draftsight CAD produced paper templates for bulkheads, etc. You can also have a shop like Kinko's enlarge the drawings.

The mockup is constructed from double wall corrugated, 1/4 inch plywood and Doug Fir 1 x 2's. One side will be sheeted with construction cardboard bought in rolls at Home Depot. Everything can be painted with house paint. It is coming along nicely, I'll post some more detail when the project is finished. In the meantime here's a couple photos.

Vince Homer
 

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blane.c

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Radials look cool but are otherwise overrated. Use engines that make aeronautical and financial sense.
 

Jay Kempf

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A half scale B25 would be a hoot. I have looked at it over and over again. But your feet end up in the front Plexiglass bowl :)

Would be an interesting show stopper at Oshkosh or SNF.

Scaling it up for a couple Yamahas would make it QUICK! Whatever scale works out to about 36' span means it fits in a T hangar and can carry the wife and baggage.
 

Jay Kempf

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Just noticed the piñatas in the shape of numerous engines hanging from your ceiling! Nice.
 

vhhjr

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The seats, panel, yoke, rudder pedals, etc will go in in a few days. The nose gear is finished and retracts as advertised, although it does rotate 90 degrees to fit under the pilot's seat.

It's plenty wide enough, but I am a little concerned about head room. That can be fixed by "talling" up the fuselage by a couple inches, nobody would notice.

M14Ps are way too large in diameter. If you look at the scale table (there's an error in the 50% power and weight numbers) you see that at a general aviation wing loading of 12 lb/ft2 you get a gross weight of about 1900 lbs. Then at 10 lb/hp you need 190 hp or 100 hp per engine. To get decent single engine performance you actually need something in the range of 14 lb/hp or 135 per engine. That's in the range of a Jabiru 3300 or both the Verner and the Rotec although it would be almost 200 lbs lighter with Jabirus. You just need an external; sound system to play radial noises. I agree, with money no object, radials are the way to go. I hadn't thought of a Kickstarter campaign, great idea.

Vince Homer
 

wsimpso1

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I like the idea!

Any good modern engine will sound wrong, except maybe a couple LS....

I would think that you would pull a swingover canopy out of a single plexiglass bubble, then apply olive tint to make the "frame" shape less obtrusive. Same for the nose bowl. I am sure you could mockup a bombsight and nose gun to conceal the rudder pedals. So, does the baggage go in and out of the bomb bay?
 

vhhjr

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The canopies are the first cut at how to get in and out of the cockpit. The real B-25 had a bottom hatch, but there's not enough room for one in the 1/2 scale. The red is primer, I have zinc chromate green for the interior and the out side will be aluminum. The windows will be clear plastic and that will be covered with silver reflective film on the passenger canopy where it's supposed to be aluminum.

Keep in mind that this is a mockup and does not represent the actual construction scheme should it ever get built. I would hesitate to build something like a B-25 with wood construction.

Vince Homer
 

Riggerrob

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Dear vhhjr,
You are off to a good start!
It will be fascinating to watch fly.

To date, only a handful of multi-engined, sub-scale replica airplanes have been built and flown: Boeing B-17 Flying Fortress, deHavilland Mosquito, Lockheed P-38 Lightning and Westland Whirlwind.

The 1/3 scale, all-metal B-17 was built by American Jack Bally and powered by four Hirth engines each producing 60 horsepower.

The half-scale Mosquito was built by a group of Frenchmen. The airframe is all wood and it is powered by a pair of horizontally-opposed engines (Lycomings?). They only had to cheat a little on canopy size and the engine cowlings. Since some original Mosquito fighters had exhaust flash-hiders (that vaguely resembled the cheek cowlings on Formula 1 racers) they just made cheek cowlings a bit bigger.

The all-composite P-38 replica was built by a Californian, but proved under-powered by a pair of converted auto-engines.

The 2/3 scale Whirlwind replica was built in New England during the 1970s, around the wings and tail surfaces from a Grumman American/ Bede Yankee. The engines were based on VWs. Mr. Butterworth sold a few sets of plans and at least 3 people started building Whirlwind replicas.
 
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Tiger Tim

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...then there’s this stunning one-off 7/8(?) scale P-38 with a pair of real airplane engines hidden in those cowls. You would win every poker run and pancake breakfast in a ride like that.
1607111790714.jpeg
 

blane.c

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When I was co-pilot on the DC-4 there were a bunch I am not sure how many people that filmed it and recorded the engine sounds for an entire day of flying start ups to the last shut down so I know there is a lot of sound footage out there, they were almost exclusively European, Americans typically don't like to get dirty when they touch an airplane. The "4" had Pratt 2,000's which have a nice Staccato. There were some DC-3's (A super "3" variant that there are many kinds of) being operated with Wright single rows Wright Cyclone R-1820 They were 1500hp models off of I think
Grumman S-2 Tracker - Wikipedia and those same guy's recorded them too. They have a nice raspy noise to them.
 
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BJC

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...then there’s this stunning one-off 7/8(?) scale P-38 with a pair of real airplane engines hidden in those cowls. You would win every poker run and pancake breakfast in a ride like that.
Yup. For more photos, see the link in post #14.


BJC
 

sming

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Hmm p-38... I always wondered if you could do something interesting by buying 1 full rv8 kit + 2 fuselage kits 😄 and do a mash-up. The spirit would be there!
 

Jay Kempf

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If that is the same P-38 scale replica I am thinking of it is just barely a 2 place and has two 1000cc Kawasaki motorcycle engines. Total one off. Amazing feat.
 
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